The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Regulatory restrictions on diesel engines include restrictions on emissions. Advanced combustion strategies are developed in order to manage these emissions. Various after-treatment systems, such as diesel particulate filters, urea-selective catalytic reduction devices, NOx aftertreatment systems, diesel oxidation catalysts, and lean NOx traps, may be used to reduce emissions to meet the emission regulations.
Low temperature combustion (LTC) is one technology to reduce the engine-out NOx emissions. FIG. 1 graphically illustrates emissions related to diesel combustion and the effects of temperature and low load operation, in accordance with the present disclosure. As illustrated, NOx emissions increase with an increase in combustion temperatures. Using exhaust gas recirculation (EGR), a method known in the art wherein exhaust gas is recirculated through the combustion chamber to introduce an inert gas into combustion process and thereby lower combustion temperatures, NOx emissions are significantly reduced. However, the HC and CO emissions may increase due to the lower combustion temperature. In particular, HC and CO emissions can become undesirably excessive at idle or low load operation during cold start conditions. As is well known in the art, aftertreatment devices require a particular temperature range in which to operate in order to be effective. Since the exhaust gas temperature is very low at these conditions, the after-treatment systems cannot reach temperatures effective to oxidize HC and CO.